Patent GB-704532-A (GB)
Title: High power electron discharge device
IPC: H01J21/06
Filed: 1950-03-15
Abstract: 704,532. Thermionic valves. RADIO CORPORATION OF AMERICA. March 15, 1950 [March 17, 1949], No. 6518/50. Class 39(1) In a high frequency high power output triode, the cathode and grid both consist of a cylindrical array of vertical rods, each rod being mounted inflexibly at one end, and independently tensioned at the other. Fig. 6 shows how each cathode element is recessed into a beam-forming electrode 2 at the same potential, in front of which are disposed the grid elements 3, each of triangular cross-section. Each cathode element is inflexibly attached at its lower end, as at 7; at its upper end it is attached to a device 82 comprising a large number of thin laminations joined together rigidly at each end. The device can thus flex in a plane perpendicular to the laminations, so allowing each cathode element freedom of lengthwise movement due to expansion. Each cathode element is maintained under tension by a spring 63 urging a small pointed insulator 72 against an arm 71 which is pivoted at 56 and transmits the thrust at 68. Each spring 63 is contained in a tube 62, arranged circularly in a base ring 73, Fig. 8. The attachment at the lower end 7 is by the method shown in Fig. 9; the cathode element 1 has a knife edge 77<SP>1</SP> which seats in a V-shaped groove 79 in a block 80. The grid elements are similarly mounted, except that they have the flexible mounting 10 at the lower end instead, contact being finally brought out to a grid terminal ring 51. The lower ends of the cathode elements 7 are attached to a cylindrical extension 30<SP>1</SP> of a lower cylinder 30 forming part of the external casing, and which connects to a ring 24 forming one external cathode terminal. This is insulated from the other cathode terminal 25. which makes contact via a flexible diaphragm 26 to a tubular central member 13 having a tubular extension 13<SP>1</SP> carrying a ring 56 to which is attached the upper laminated flexible mountings of the cathode elements. The upper ends of the grid elements are attached by the method shown in Fig. 9 to a hat member 12; this is separated by an insulating ceramic member 11 from a support 53 which is attached via a mounting member 45, perforated to facilitate exhausting, to the main support 55 of the upper ends of the cathode elements. The ceramic member 11 is silver soldered or copper brazed to the metal members 12 and 53, these latter being divided into separate fingers where they are joined to the ceramic, so that the stresses resulting from the thermal expansion mismatches of metal and ceramic do not exceed the rupture strength. The cylindrical anode 4 surrounds the entire cylindrical array of cathode and grid elements; it is closed at one end by a cap 52, and at the other end is turned back upon itself as at 21', extending via a lead cylinder 21 to the anode terminal ring 23. The anode has longitudinal water channels 14, which may be slightly spiralled, closed by a snugly fitting outside cylinder 44. The anode cooling water enters through inlet 38, flowing down through the annular space 41 between cylinders 21 and 44, to the region 42, where its direction is reversed, now passing up through the anode channels 14 into the space 43; and out through tube 39. A separate water-cooling flow for the internal structures enters by inlet 32, passing downward through channel 36 where flexible diaphragm 26 is cooled. The water then flows upwards through the annular space 35 between the tubular central member 13 and a water partition 31, and then down through the annular space between the water partition and cylinder 17, which is an upward extension of cylinder 30. A copper helix 132 wound outside the partition gives a spiral motion to the water, which is withdrawn through outlet 33. This water flow is also utilized above the ledge 108 to cool a sleeve 106 conducting heat from the cathode mounting. The sleeve surrounds a recessed portion of extension 13<SP>1</SP> having partitions 107 forming channels 107<SP>1</SP> which communicate with one another over the upper edge of partitions 107. Water thus travels from channel 35 up by passages 109 and alternate channels 107<SP>1</SP>, through holes 110 into channel 34. The beam-forming electrode 2 is positioned with respect to, and insulated from, the composite central structure 13, 13<SP>1</SP>, 106 by a seal 28 formed by an appropriately shaped array of concentric metal sleeves 58, 59, 60, 61 sealed with glass as at 65. The outer envelope is demountable, comprising a number of separate sections bolted together. The vacuum-tight joint at 111 consists of a gasket 91 of copper or other soft metal, squeezed between the polished surface of ring 111 and the beaded surface of flange 96 under enormous pressure. The bolts 92 and nuts 94, 97 are of special steel, heat-treated so as to withstand the high temperatures and tensile stresses. The construction of the demountable joint at the anode terminal 23 is similar to that at ring 111. The demountable joint at the grid terminal ring 51 may again be similar, but a different arrangement is shown in Fig. 3. Brazed into grooves in the upper and lower surfaces of ring 51 are rings 116, 116<SP>1</SP> made of the alloy known under the Registered Trade Mark " Vega ", the rings being coated first with copper and then silver. Flanges 19, 20 are of copper-plated steel. The adjacent abutting surfaces of flanges 19, 20 and rings 116, 116<SP>1</SP> are highly polished, and between them are placed copper wire gaskets 117, 118, 118<SP>1</SP> which seal under pressure when nuts 94, 97 are tightened on bolts 92. The electrodes may be in everted arrangement, or planar. Some typical dimensions and operating data are given. U.S.A. Specification 2,427.597 is referred to.